


Childish Concerns

by kuro1neko2kun



Category: Mortal Instruments Series - Cassandra Clare, Shadowhunters (TV)
Genre: Alec is a suspicious cupcake, Gen, Luke is (eventually) good at advice, Magnus doesn't know what to do with them, Simon is okay at dealing with kids, Simon is wrapped around Izzy's tiny fingers, The one where the Lightwoods get turned into preschoolers
Language: English
Status: In-Progress
Published: 2016-03-07
Updated: 2016-04-05
Packaged: 2018-05-25 06:48:34
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 8
Words: 7,920
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6184828
Author URL: https://archiveofourown.org/users/kuro1neko2kun/pseuds/kuro1neko2kun
Summary: <blockquote class="userstuff">
              <p>Alec, Jace and Izzy get de-aged by magic. Simon and Clary are stuck looking after them while Magnus works on a cure.</p>
            </blockquote>





	1. In Which Simon Asks the Logical Questions

**Author's Note:**

> fill for [Shadowhunters Ficathon](http://ladygawain.livejournal.com/83265.html?page=6#t1023553)

Clary isn’t sure how it happened. All she knows is that she looked away for like two minutes to finish off the Ifrit demon she was fighting and when she turned around, there were three tiny sleeping children where Jace, Alec, and Isabelle had been standing. Fortunately that had been the last demon, because Clary was pretty sure tiny Jace, Alec, and Isabelle would not be able to handle it. Staring at her friends blankly for a moment, she jumped when a car horn sounded from outside the alley they’d been fighting in. Glancing around furtively, she took out her phone. It wasn’t like she could very well pick up all three of them by herself.

She called Magnus first. Mainly because he was more likely to know how to _fix this_ , before things got even more dicey. There really wasn’t time for this, not with Valentine still on the loose. Tiny Alec sighed and started to move and Clary panicked. 

“ _Hello?_ ” Magnus’s voice brought her out of her panic somewhat.

“Magnus! Help! I turned away for like 3 seconds and when I looked around again… yourboyfriendgotturnedintoachildandIdon’tknowwhattodo! Magnus! What am I supposed to do with three children?”

Tiny Alec woke up with a start, jumping to his feet and looking around suspiciously (looking alarmingly adorable as he did).

“ _What? I could have sworn you said-_ “

“Who are you?” Alec’s eyes were narrowed at her suspiciously, “What did you do to Izzy?” He was standing protectively in front of his sister.

“Help! Just-” Clary shoots a look at Alec, “Come to the alleyway behind the docks. Quickly!” She hung up and pressed her second speed dial, calling Simon.

Tiny groans started to sound from where Jace was collapsed, and Clary cautiously moved towards him, noting that Alec’s eyes were following her.

“ _Clary? I thought you were out hunting._ ” 

“Um. I was. But. Something happened.” Clary crouches over Jace’s tiny body, “I need your help.”

“ _What about Jace? I thought you were with the badass Shadowhunters._

“That’s kind of the problem…” Clary jumps back just in time to avoid Jace’s head crashing into her forehead, “I need you to come to the Alley behind the docks. Preferably ten minutes ago.”

Jace’s blue eyes are narrowed as he glances mutely between her and Alec.

“ _Fine, be there in a flash._ ” 

A portal opens behind her and Magnus steps out, taking in the scene before him. Clary almost lets out a sigh of relief.

“You weren’t kidding Biscuit.” He steps towards Alec, who produces a seraph blade almost as long as his entire body from…somewhere. Magnus steps away with a flinch, “You didn’t see anything weird when they changed?”

“I looked away for less than a minute, and then they were like this!” Clary detects a hint of hysteria in her voice, and Alec’s tiny eyes widen as he struggles to keep the seraph blade up.

“Alexander,” Magnus is looking back at his miniaturized boyfriend, “Do you remember what happened at all?”

“Who are you?” Isabelle groans as Alec is speaking and he glances back and forth, suspicion still embedded in his tiny features.

"I'm Clary and this is Magnus," Clary gestures between herself and Magnus, keeping her movements slow, "We're here to help you."

"Where's mom?" Clary wonders why Alec isn't asking for his father, but everyone's attention shifts when Isabelle starts to sit up, blinking in confusion.

 

“Alec…?” She wobbles slightly and Alec rushes to crouch beside her, visibly straining to keep the tip of the blade between them and Magnus.

“Shhh, Izzy,” He pats her head with his free hand. Jace is still strangely silent.

Simon appears in a whoosh beside Clary, and both Alec and Jace jump.

“Clary, what-?” Simon’s gaze lands on the tiny Shadowhunters and he stares.

“Exactly.”

"I see what you meant by problem…" He sighs, "How old are they?"

"I don't-"

"I'm six." Alec speaks up from where he's helping Izzy sit up, seraph blade set to one side for now.

Clary does the math in her head. If Alec's six, that would make Jace five and Izzy… Clary wants to wring the neck of whoever did this. She cannot deal with a four year old. The one time she'd dealt with preschool kids, she'd gotten tied to a chair and covered in mashed bananas. 

“Well, we can’t fix any of this in an alley,” Magnus wrenches his gaze away from the Lightwood siblings, “Best get them somewhere safe. The perpetrator might still be around, not to mention the other dangers lurking in dark corners.”

“We can’t take them to the Institute!” Clary frowns, “Lydia is still there, and I don’t want to know what would happen if she found out about this. They’re already in enough trouble with the Clave.”

“They can’t stay at the Hotel Dumort, and my mom is still…” Simon shrugs.

“I suppose…” Magnus taps his chin with one manicured finger, “I suppose my place will have to do. I know I said I wanted Alexander to come by more, but I’m pretty sure this isn’t what I meant.”

“How are we gonna get them there?” Simon glances at Alec, who’s still glancing between them with suspicious eyes.

“Um…” Clary follows his gaze.

“Portal?” Magnus waves a hand, a portal appearing on one of the walls. 

“You-“ Alec is speaking up, eyes fixed on the portal, “You’re a warlock?”

“Yes, I am,” Magnus grins at the child and wiggles his fingers, sparks trailing after them.

“Mom says downworlders are bad guys,” Izzy is speaking up for the first time, tiny voice filled with doubt.

Magnus flinches, eyes flashing gold.

“Downworlders aren’t all bad,” Simon is speaking up, and Clary glances at him in surprise. Barely a month ago, he was the one claiming that he was a monster and she should stay away, “Some of them are really nice. Like Magnus. He’s a nice warlock."

“Are you sure?” Izzy’s eyes narrow as she considers Simon’s claim.

“Of course! Downworlders are like…” Simon glances around, Clary assumes for inspiration, “Plants.”

Magnus raises an eyebrow at the vampire, wondering if he should feel offended.

“Some plants are poisonous, yes, but some plants you can eat. Downworlders can be bad, like poisonous plants, but some of them are good, like edible plants. You like fruits right?”

Isabelle nods solemnly, “Strawberries are my favourite.’

Alec looks like he’s mulling over Simon’s words.

“Magnus is like a strawberry!” Simon is grinning, and Clary snickers under her breath. Even Jace is looking over with some interest, although he’s still quiet, "Even though he's a plant, he's not poisonous and he tastes good."

“Hey-“ Magnus begins to object, but quiets when Simon shoots a glance over at him. He resolves to get the vampire back later.

“I like strawberries,” Alec says quietly, looking between the adults. Clary fights the urge to coo at the adorableness, and Magnus’s eyes widen when Alec nods decisively and announces, "Strawberry downworlders are fine.”

Clary regrets not having her phone out to take a video of the declaration.

“Guys-," Magnus gestures at the portal. 

"We'd better go," Simon glances around, taking a step towards the Lightwood siblings, still huddled together on the ground. Alec snatches up the seraph blade.

Simon glances at Clary with frustration and she sighs, leaving him to collect Jace as she nears Alec slowly, hands up in the most unthreatening manner she can manage. 

"Alec, can you put down the sword for me?" Clary inches closer and Alec hesitates, "I need to carry Isabelle through the portal, and for that I need to come closer."

"Where are you taking us?" Alec is trying to glower, but what looks impressive on a man who is 6 feet tall with tattoos and bulging muscles is just endearing on tiny Alec. Clary suppresses a smile and gestures back to Magnus, ignoring Simon's low muttering to Jace.

"I'm taking you to Magnus's house. Something happened to you guys and he's going to help us fix it." 

"Why can't we go to the Institute?" Alec lowers the blade slowly, and Clary crouches down in front of them.

"Your parents are really busy right now, and Magnus is going to have to take a look to check what went wrong," Clary reaches slowly for Isabelle and startles when Alec drops the seraph blade and swings his sister into his arms with a grunt.

"I'll take care of Izzy." Simon better be having more luck.

"Alexander, sweetheart, Clary needs to carry Isabelle so that no one gets lost in the portal. You can stay with them, but you need to let Clary do it." Magnus's voice is slightly strained, and Clary glances at him apologetically. 

"I don't know…" Alec looks between them and then huffs, relinquishing his sister to Clary, "Don't drop her or I'll… I'll… I'll do something."

Simon has Jace standing up and holding his hand, and Magnus gestures for him to pass through the portal as Clary is standing up with Isabelle carefully braced on one hip.

"See you on the other side." Simon ushers Jace through the portal with a wave to Clary, and Magnus's eyes transition to the cat's eyes he usually covers with a glamour.

"Alec, we need to go," Clary offers the boy a hand, "You can hold my hand the whole way through, I promise it'll be fine."

Alec glances between her and her hand for a moment before he takes it, both of them making their way to the portal. She glances back at Magnus before stepping through, and he waves.


	2. In Which Fun is Had by (Almost) All

When they get back Magnus leaves Simon and Clary to sort out the kids, retreating into his study to look through his books. He snaps a couple toys onto his coffee table, sending a quick grin to Alec, who's eyes have lit up at the display of magic.

"So…" Clary glances between the children and then settles on Simon, "What do we do now?"

"Um." Simon turns to the kids, "Do you want to play Lego?"

Jace kicks his feet against the couch, and Alec shrugs.

"What's Lego?" Izzy asks innocently, and Clary wonders what it was like for them when they were actually children, that they don't even know what Lego is.

"It's blocks that you can stick together to build things with!" Simon picks up a box full of lego pieces and demonstrates.

"What's the point?" Jace scowls at them, "You can't kill demons with blocks."

"It's fun!" Clary tries to smile encouragingly, and Jace just shrugs.

"Shadowhunters have no use for fun."

"How do you play?" Alec looks curious, but is still sticking close to Izzy.

"You think of something you want to build, and then you try to put it together using the blocks!"

"Boringgg," Izzy announces, sticking her tongue out, "I wanna play Demon catch."

Alec is torn between wanting to try out the Lego and sticking close to his sister.

"What's um- Demon catch?" 

"Someone pretends to be a demon, and then you gotta catch them." Izzy grins at him, somehow looking menacing even as a four year old, "You be it."

"Izzy…" Clary glances at Simon out of the corner of her eye. Jace sneaks out a hand and pinches Alec in the side. He frowns and turns to glare at the other boy.

"Demon catch, demon catch, demon catch!" She stands and starts stalking towards Simon while Alec is preoccupied. Simon sighs in resignation.

"Alright. Alec, Jace, are you two playing too?" 

"I don't wanna play with a baby," Jace pouts, and Alec glances between his sister and Simon nervously.

"I don't-"

"You can play Lego with me if you want." Clary picks up a block and offers it to him. 

Jace hops off the couch and takes a block from the box, turning it over to examine it between his tiny hands. Alec glances at Izzy, pouncing on Simon, and sighs, accepting the block.

"What are you going to build?"

"I'm gonna make an Institute." Alec, now focused on his new task is starting to sort through the coloured bricks, looking for the ones he wants to use. Clary smiles and stifles a snicker as she sees Simon being put in a headlock by Isabelle.

"I'mma make a better Institute!" Jace announces haughtily, pushing Alec's hands away and going through the box of Lego himself. Alec frowns at him.

-

An hour later, Simon is lying on the couch with a tired Izzy sprawled across his chest, both of them already half asleep. Clary is trying to separate Alec and Jace yet again, their latest argument having evolved into shouting. She's pretty sure they're overtired. They've already had to deal with Alec's freak out when he realized he was letting his sister play with a _vampire_ , and all of the little squabbles between the two boys. Luckily Izzy was relatively well behaved, if insistent on getting her way.

Magnus had peered out the first time he'd heard shouting, but quickly returned to his office when he'd seen Clary dealing with it (she's jealous that he had the luxury). She suspects he put a silencing spell on the door, because he hadn't come out since.

Clary has a stamina rune burned on her hip, only the second time she's used it (and the only time she ever wants to need it to deal with this particular problem). 

"He took the last blue block!" Alec is frowning at her from where she'd placed him in a corner. From the opposite corner, Jace blows a raspberry. Clary groans. Of course Jace was a trouble child. 

Izzy's nose wrinkles and her eyes start to well up with tears at the noise.

"Shhhh," Simon is panicking a little bit, patting her on the back and looking at Clary helplessly. She sighs.

Glancing at the clock, it registers that it's almost three in the morning. 

"Alright, wow, it's really late," Clary frowns. Magnus only has one guest room and she doubts she'll be able to put Jace and Alec together without tears. If the last few hours have been a representative sample of their behaviour, she's pretty sure that would end in tears.

"Time to get you guys to bed," Simon is sitting up, adjusting Izzy in his arms and feeling grateful for his vampire strength. The bed problem occurs to him just then and he pauses.

"Um. Alec and Izzy could take the bed with one of us, and the other can stick with Jace out here?" She looks at the door to Magnus's office. 

"I don't wanna sleep with him!" Alec is making a face, "He might eat me!"

Apparently his newfound acceptance of Downworlders isn't quite enough to make his sleep with Simon. Clary sighs at Simon's flinch.

"I'll take these two, you take Jace?" He stands up, still holding onto Izzy who's already half asleep.

"Alright, fine." He hands her over and Clary accepts her, glancing at Jace in his corner.

"I'm not tired." _Of course Jace is going to make this difficult._

Simon groans. Alec yawns widely and rubs one bleary eye.

"Alec, c'mon, time for bed." Clary shifts Izzy onto her hip and holds a hand out for Alec. 

Jace sticks his tongue out at Alec and Clary has to hold him back by the hand.

"Good luck with that," she smiles sympathetically as she pulls Alec along with her to the spare room.

Simon just sighs in response.


	3. In Which Simon has a Rude Awakening and Magnus and Alec Bond

"Found it!" 

Simon groans awake at Magnus's exclamation, peering over the edge of the couch to see the warlock (looking alarmingly awake) staring at him.

"Where's Alec?" Magnus looks concerned when he only spots Jace, curled up on an armchair where Simon had finally convinced him to close his eyes and count to a hundred.

"Mrfnglerfm," Simon points towards the spare room and rolls over, turning his back to Magnus and hoping to catch a few more hours of sleep. Thankfully Jace hasn't woken up yet.

"I assume you're referring to my guest room." Magnus waves a hand and Simon is suddenly very awake (and also wet and cold, although as a vampire the cold isn't much of a problem), "I'll go check on them while you get breakfast. I think waffles today."

Simon scowls, wiping his face. He sits up just in time to see Magnus disappear into the guest room.

-

Magnus peers into his guest room carefully and finds a six year old staring back at him. Isabelle and Clary are still asleep, their soft breaths whooshing in the silence. He steps into the room, closing the door behind him to block out Simon's sputtering. Alec's hazel eyes follow him, a spark of wariness still lingering.

"Hey there," Magnus smiles at him, and Alec slips off the bed, standing between him and the girls.

"Are you gonna wake them up?" His eyes are wide, presumably having heard what happened to Simon, "They were really tired..."

Magnus's hands flutter as he tries to figure out what to do. "I suppose I can let them sleep in…"

"Thanks." Alec smiles at him, and Magnus feels like the sun is coming out from behind the clouds, same as when big Alec smiles (although he has a feeling Alec's smiles got rarer as he aged).

"Do you want to come out and play so that we can leave them to sleep?" He's gesturing awkwardly at the door behind him and Alec looks back at his sister's sleeping face before nodding, stepping forward and reaching for Magnus's hand.

Magnus lets him take it, fingers limp in Alec's tiny grasp, and leads him out of the room, setting a muffling spell on the door. Alec had asked to let them sleep after all… 

Simon seems to have (begrudgingly) gone to acquire breakfast, and Jace is still asleep on the armchair. Magnus puts a finger to his lips and leads Alec to his own bedroom, closing the door behind them as Alec looks around curiously.

"What do you want to play?" Magnus sits on the edge of his bed, patting the spot beside him for Alec. 

"Um…" Alec climbs onto the bed, bumping into Magnus's knee as he does, "Can you read me a story?"

"Of course." Magnus smiles and snaps his fingers, summoning a Dr Seuss book from a nearby Barnes and Noble. Alec's eyes widen.

"Is that- Magic?" Magnus practically melts inside at the excited look he's getting.

"Of course," Magnus snaps his fingers again, summoning a sunflower and offering it to Alec, grinning when Alec accepts it with excitement, examining it from all angles, "I am the High Warlock of Brooklyn after all."

"Does that mean you're the most magical Warlock in Brooklyn?" Alec is practically bouncing on the bed in excitement, and Magnus sets the book aside for a moment, swirling his hands through the air to conjure a flurry of sparks, shaping them into a bow and arrow. 

"Yep!"

-

Clary finds them a few hours later, Magnus lying on the bed curled around Alec, with tiny stars dancing above their heads.


	4. In which there is a small disagreement

Things between Alec and Jace come to a head on the tenth day, a fight escalating during playtime with blocks (again). Simon's out checking in with Raphael and Magnus is in his office, leaving Clary taking a nap in the guest room with the door cracked open.

Alec is building a tiny model of the City of Bones, Isabelle sitting quietly beside him to watch. 

“I bet you’re a sucky Shadowhunter,” Jace pipes up from his spot on the couch.

Alec ignores him.

“I’ll bet this whole thing is all your fault.”

His teeth grit together, fingers clenching around the block he’s holding.

“You take that back!” Izzy pulls herself to her feet, wobbling a little as she approaches Jace.

“Hmph. You’re both too soft.” Jace sneers at her, shoving her away, “I bet you haven’t even killed your first demon yet.”

“Well-“ Izzy puffs up her cheeks, frowning up at Jace, “You’re a big meanie. I bet you have no friends because nobody likes you!”

“I don’t have friends because attachments make you weak!” Jace jumps to his feet and shoves her, pushing her to the ground with a cry.

Her eyes well up with tears and Alec steps forward with a frown.

“You can’t talk to her like that!” Alec pulls her to her feet and steps between her and Jace, standing close enough to see the flecks of green in his eyes.

“What are you gonna do about it?” Jace sneers, the expression out of place on his tiny face, “Cry to your mommy?”

“You’re just a big bully!” 

“Momma’s boy!” 

“Dummy!”

“Suck up!”

“Stupidhead!”

“Sissy boy!”

Izzy gasps when Alec lunges forward, landing a punch square on Jace’s nose.

Jace lets out a startled gasp when Alec pulls back, hands coming up to prod at his nose. They come back covered with blood.

“You broke my nose!” He stumbles back and starts wailing as the pain hits him.

-

Simon returns to utter chaos, both Izzy and Jace wailing while Alec tries to comfort Izzy.

The smell of blood hits his nose second and he pauses, closing his eyes to gain control over his impulses.

“CLARY! MAGNUS!” 

“Simon, what-“ Magnus peeks his head out of his office and starts at the sight of blood.  
“Oh my God!” Clary, finally up from her nap, rushes forward, crouching down in front of Jace with concern, “I closed my eyes for like two minutes!”

“What happened?” Magnus approaches hesitantly, wincing at the grating sounds of crying. He snaps his fingers to summon tissues, handing them to Clary and making a face at the blood on his floor. At least it’s not carpet. He snaps again, clearing away the blood.

“He bwoke mah nothe!” Jace’s voice is thick, nose plugged with blood, as he points one hand at Alec. Clary pries his other hand away from his face to take a look.

“How? Why?” Simon edges around, breathing shallowly, to pick up Isabelle, patting her on the back gently as he extricates her from Alec’s fluttering. Alec protests, but quiets when Clary turns her attention onto him, shrinking back.

“Alexander Gideon Lightwood, why one earth did you break Jace’s nose?” She exchanges a look with Magnus and he sighs, beckoning Jace closer to deal with his nose, leaving her to stand and level a stern look down at Alec.

“He deserved it,” Alec says under his breath, avoiding looking up at Clary.

Isabelle’s wails have quieted, and Simon retreats to a corner with her, trying to ignore the blood in the air.

“Why did he deserved it?” Clary frowns at him when he remains stubbornly silent. “Alec, look at me and answer the question.”

“He was being a meanie.” Alec stubbornly stares at the ground.

She hears a snap behind her, and Jace’s breathing shifts back to normal.

“Why did you break his nose?”

“He pushed Izzy.” 

She lets out a breath through her nose. Magnus frowns.

“Jace, did you push Izzy?” Magnus looks down at the boy, blood still all over his face.

“Tattletale,” Jace mutters under his breath, and Clary has to restrain the surprisingly strong six year old from launching himself back at Jace.

“I see.” Clary rubs her temples to deal with the burgeoning headache, “Fighting is not the way to solve your problems, boys.”

Both of them huff, and Simon snickers at their almost identical put upon expressions. She sends a stern glance at him.

“Seriously. Both of you are in big trouble right now.” Magnus makes a face at her (thankfully out of the boys’ sign lines), and Clary sighs. How is she the only actual adult in this situation?

“It’s his fault,” Alec mutters.

“Nuh uh.” Jace is sticking out his tongue.

“Yeah huh.” Alec sticks his tongue out in return.

“Nuh uh.”

“Yeah huh.”

“That’s it!” Clary raises her voice to interrupt them, and releases Alec to point at corners in opposite sides of the room, “Time out! Alec, Jace, you’re both going to stand in different corners and think about why you should not punch people in the face,” She levels a stern look at Alec, “Or call people names.” She sends a pointed glance at Jace.

The boys retreat to their corners sulkily, sending sideways glares at one another the whole way


	5. In Which Time Passes, and Luke Passes on Some Wise Dadvice

As it turns out, Magnus's solution is going to take a month to prepare. Clary is ready to tear her hair out stressing, while she watches the miniaturized Shadowhunters, and Izzy has Simon wrapped around her tiny finger. Alec and Jace still aren't getting along at all (and Clary wonders how they even ended up as parabatai if this is how they acted around each other when they were actually kids). 

Magnus had created an extra bedroom out of the broom closet on the third day. (Clary's not asking questions, she's just happy no one was sleeping on the couch anymore). 

Magnus can't be trusted to watch the kids alone. Not that he'd let any harm come to them. But he just couldn't be trusted not to do whatever stupid idea the kids suggested, and after catching him summoning a lesser demon for Alec to pet on the seventh day, she instituted a _no unsupervised magic around the children_ rule. Simon was slightly better with the kids, although the minute tears started to well up in Izzy's eyes he was a useless wreck. Clary had never been more glad for coffee and stamina runes.

By the twelfth day, Clary gives up and calls Luke, putting 101 Dalmations into Magnus's brand new entertainment system for the kids to watch (it was the only movie they'd agree on, because Izzy linked the dogs, Alec liked the music, and Jace appreciated Cruella Devil's drive enough to not be a terror while it was playing- unlike the Aristocats, which is the reason Magnus had needed a new TV in the first place. Apparently Jace and ducks did not go together at all).

-

" _Clarissa?_ " Luke's voice is a welcome change, and she almost spills everything right there and then. After the nose debacle, they hadn't left the kids alone for a second, and it was really wearing on all of them (but mostly her and Simon).

"Luke! You're good with kids, right? I need your advice." Clary eyes the kids sitting calmly on the couch for once, feeling like she's in the eye of a storm.

" _Kids? Clary, what-?_ "

"How do you make them behave?" She interrupts him before he can ask why she needs to know.

" _Bribery, I guess._ " Luke's voice is equal measures fond and confused, " _Always worked on you, and Simon too when I had to deal with them. If you want 'em to do something, tell them they'll get something in return_."

"Isn't that a little-" Clary glances over at Simon, bent over the coffee table with his head in his arms. Okay, maybe bribery is a good idea.

" _Yup. Always works. But seriously, why are you asking about-_ "

"How do you deal with temper tantrums?" She interrupts, glancing at Jace, and Simon shoots a tired grin her way.

" _Don't pay them any attention._ " They have an agreement about Shadowhunter business, he won't ask and she will tell him if things go south. Clary's pretty sure he'll understand why no one can know about the kids, but she still can't tell him. Not when he has to deal with the expectations of his pack on top of everything else, " _If they insist on making a spectacle of themselves, make it clear that that's not getting them anywhere, just leave the room._ "

"Thanks Luke!" 

" _Clary, you haven't-_ " 

"Bye!" She hangs up before he can ask and slumps forward against the table, mirroring Simon.


	6. In Which Jace is a Brat and the Lightwoods have a Bath

**Summary for the Chapter:**

> The one with Simon and Jace bonding that no one asked for.

“Jace, you haven't eaten anything." Clary looks over at Jace's plate and he scowls at her, poking his uneaten spaghetti and meatballs with a fork.

"M'not hungry." 

"Come on, just a couple bites?" Clary tries to best to look encouraging, pointing to Alec and Izzy, who are finishing up their own plates (Simon is helping Izzy, but Alec is eating on his own, fork awkwardly clenched in his too small hands).

“I don’t WANT to!” 

“Jace, come on, you need to eat,” Simon sets aside Isabelle's dinner to deal with the newest tantrum. Isabelle pouts.

“No!” Jace is already starting to turn red with frustration, and Clary fondly remembers the alley he’d first been changed, where he hadn’t talked at all.

“C’mon buddy, at least eat a little bit?”

“It’s gross!” Simon sighs at the response, running a hand through his hair.

“Why don’t you like it?” 

Jace just sticks tongue out and blows a raspberry. Clary throws up her hands in exasperation. Simon runs a hand through his hair, getting a smear of sauce on his forehead.

"Alec and Izzy liked it just fine! I made it myself, there's nothing wrong with it!" 

"I don't like it!" Jace's face is starting to redden with frustration.

"At least eat one of the meatballs?" Clary tries for cajoling.

"NO!" 

Clary ducks under the spaghetti that Jace throws, plate and all, right at her head.

"Why you little-" Simon stands, interrupting her in the middle of her wind up.

"Clary, why don't you take Izzy for a bath," He steps towards Jace, and she nods gratefully, collecting Izzy carefully so as to not get any of the spaghetti sauce covering the girl onto herself.

Jace is a monster. He never listens, he’s ridiculously picky about everything, and he’s constantly making trouble. Clary’s already had to clean up spilled drinks, thrown food, and deal with like a million tantrums. She’s almost glad to hand him off to Simon and take Isabelle for a bath, Alec trailing along behind her. 

Simon is looking more and more worn around the edges, between the little sleep, his relatively recent transformation, and the energy requirements for taking care of three hyperactive shadowhunter children all wearing at him. But Jace mostly behaves for him. Sort of. Well. He's better behaved for Simon than he ever is for her. She turns on the water after setting Izzy down on the toilet seat, Alec closing the door behind him.

"Are you gonna have a bath too?" Isabelle is beaming at Alec as he leans against the door, and Clary mentally coos at them. It was obvious from her first meeting with them, how much these two care about each other, and their sibling bond is very clear. 

"I don't-" Alec glances warily at Clary and she shrugs. Although Simon had been taking care of most of the baths, she had bathed Isabelle a couple times.

"C'mon, it'll be fun!" Isabelle manoeuvres her way off the toilet to tug at Alec's shirt. He sighs and gives in with a last glance at Clary, clearly choosing the path of least resistance. Clary shuts off the tap and tests the water one last time to check the temperature. _Perfect._

"Alright then, everyone who's having a bath had better get in now before the water gets cold!" She descends on Izzy with a grin, helping her out of her clothes. 

Alec stiffly steps out of his own clothes and into the bath, relaxing when Clary smiles at him reassuringly before lowering Isabelle into the tub with him.

-

Simon and Jace have a stare off while Clary herds the Lightwoods into the bath, only breaking eye contact once they hear the door close.

"Jace-" Simon steps forward slowly, and Jace scowls at him.

"I don't wanna be here." Simon sighs at the admission, crouching down in front of Jace's chair to look him in the eyes.

"I know this isn't home, and I know you're having a hard time right now, but we really need you to cooperate, at least long enough for us to get this fixed." Simon reaches forward, stopping when Jace leans away.

"I want my dad."

"I'm sorry Jace," Simon sighs, running the hand he'd been reaching out to Jace with through his hair, "Your dad is…busy. It's only a week or so until we get this fixed. I know this isn't easy for anyone, but can you at least try to behave? And at least be civil with Alec and Izzy?"

"I-" Jace sets his jaw mulishly, and Simon braces himself for the impending argument, "I don't want this. I just wanna go home and train with my dad."

"I know, and I'm sorry that you can't." Simon sinks down onto his heels, "I know what it's like to miss your dad, and I know this is a completely new place and new people. But I need you to understand that it's only temporary. If you at least try to cooperate, this can be easier for everyone involved. Clary and I are trying our best, but we need your help to get through this."

"What do you know, vampire." Jace snaps, looking him in the eye challengingly.

"Jace-" Simon frowns, "Come on. Just behave for the next week or so, and this'll all get fixed. Otherwise you might have to put up with me for even longer."

"I-" Jace seems to wilt a little bit, the fight slowly seeping out of him. "Fine."

"You can start by helping me clean up the mess you made." Simon stands, gesturing at the spaghetti dripping down the walls, and the shards of plate on the floor.

"Hmph." Jace hops down from his chair, looking like an angry kitten as he stalks towards the kitchen to retrieve the garbage bin. Simon follows to supervise.


	7. In Which Maryse and Robert Finally Show Up

Maryse and Robert find out on the twenty third day. Clary is kind of amazed at herself for managing to keep this from them for so long.

To be fair, they’d been in Idris for most of the month with Max. But still. Clary watched as the Lightwoods stared at one another, and wondered what it was like to have that distance from your parents. Her mom would have noticed within hours. Simon’s mom too. She glances at Simon, who’s biting his lip nervously. Magnus is standing to the side of the room, watching the tense face off carefully.

“Alexander?” Robert steps forward hesitantly, and Alec straightens his tiny shoulders. Izzy is watching everyone warily from her spot beside Simon.

Jace is suspicious, and if occurs to Clary that he must not have come to live with the Lightwoods until slightly after this age then. His lack of reaction to all of the strangers is even more worrying.

"Clarissa, what happened?" Maryse's tone is strict, and Clary sees Alec flinch out of the corner of her eye, "How long has this been going on?"

"It happened on a patrol. Magnus has been working on a cure…" Clary hopes that keeping things from them was the right thing to do, otherwise her future career as a Shadowhunter with the New York Institute is not going to pan out. Maybe she can work as an author. She probably has enough unbelievable stories by now.

"How long?" Maryse walks forward, stopping in front of Alec, who smiles at her hesitantly.

"I-" 

"Twenty three days." Simon is the worst at handling things under pressure. Clary sends him a betrayed look. He shrugs in response.

"Why on earth wouldn't you have told us about this immediately? We could have had the Silent Brothers working on this." She sends a dirty glance at Magnus, and he frowns. Alec frowns too, looking between Clary, Magnus, and his mom, who's still scolding them.

"Mom?" Alec's voice is still strange to hear, high and thin.

"Not now dear," Maryse dismisses him and Magnus and Clary both frown. Simon glances at Clary, trying to communicate with his eyes that she should definitely not do whatever she's planning to do. 

She ignores him.

"I know you're getting into a groove right now, but I think your _son_ wants to say something," Clary interrupts, holding up a hand. Izzy looks at her with wide eyes.

"Excuse me?" Maryse sounds offended. Good.

"I _said_ your son has something to say." Simon groans under his breath, and Magnus looks like he's about to add on.

Maryse pinches her lips together, turning to Alec impatiently.

"I-um-mom- y-you should be nicer to Clary and Mags," Alec finally blurts out, stumbling over Magnus's name.

"Is that all?" Maryse frowns at him, nostrils flaring, and Clary almost steps between them, a challenge in her eyes.

"No," Alec's tiny voice gains strength, "Clary and Magnus have been trying to help us and they don't need you to scold them for doing their best." Simon makes a noise, "And the vampire's been helping too."

Clary hides a smile behind her hand.

"Fine." Maryse leans back slightly, and Alec hunches his shoulders self-consciously, "Clarissa, thank you for taking care of my children while they were incapable of defending themselves. Now," She looks between the kids, "Come along, we're going back to the Institute now to see the Silent Brothers."

"Madam Lightwood," Magnus interjects, as Jace sullenly glares from his spot on the couch and Izzy pouts, "There's no need to go to the Silent Brothers. I've already found the solution, and it will only be a few days before it's prepared and I can get them back to normal. They're already comfortable here, and Clarissa and Simon have been doing an admirable job taking care of them."

"Are you suggesting I leave my children in the hands of a vampire and a warlock while they're defenceless and innocent?"

Clary bristles, and Simon grabs her by the wrist.

"I'm suggesting that you leave them in the place they've grown accustomed to for the last three days so that I- the most powerful warlock in Brooklyn- can ensure their health and safety."

"Maryse-" Robert steps forward before Maryse can start to react, inserting himself between his wife and Magnus, "Thank you for offering your services. Since you have the capacity to care for children at the moment, which the New York Institute currently lacks, please take care of our children until such a time as they can once again care for themselves."

"I shall." Magnus's shoulders have straightened and he's standing with his head high.

Maryse huffs and stalks off, Robert following behind her after patting Izzy on the head and clasping a hand on Alec's shoulder.


	8. In Which Colouring is Done and Cures are Administered

Magnus finishes the cure on a Tuesday. Alec and Jace are finally starting to get along (or at least are being subtle about their fighting), laying side by side on the floor drawing. Simon is playing Demon catch with Izzy again (although it mostly consists of Simon crawling around and getting jumped on by Izzy).

Clary grins when she catches sight of what the boys had been drawing. You can take a Shadowhunter out of the battle… Simon groans when Izzy sends a particularly enthusiastic kick right at his kidneys, and Clary winces. That's exactly why only Simon ever agreed to play demon catch with her (and only because Simon folded like a wet paper bag every time she stuck out her lower lip).

Alec reaches for a purple crayon, and Jace snickers at him, getting a grumpy look from the older boy. Okay, maybe getting along may have been too strong of a word. Clary hurried to distract them.

"Alec, Jace." She calls, standing up from her supervisory spot on the couch, "Do I have to separate you two again?"

"No," They grumble in unison, returning to their drawings. Alec's drawing is of Magnus (of course it is), fighting what looks to be a fairly accurate representation of a Shax demon rendered in yellow and green. He's added what looks like little sparkles all around, presumably to represent Magnus's magic.

Jace had drawn an Iblis demon being gorily impaled by a seraph blade, with blood spurting out of the wounds. Clary winced. Jace had some issues as a kid. Not that it wasn't to be expected, with Valentine as their only guardian, but still.

Just as Izzy was scrambling to pin down Simon's arms with her own smaller limbs, Magnus burst out of his office, smoke billowing out behind him.

"Magnus?" Simon sits up, sending Izzy tumbling down into his lap. She frowned up at him, tiny nose wrinkling.

"Oh, not to worry, just a slight miscalculation when I was setting up the vents." Magnus waves a hand airily, the smoke disappearing with a flash of blue. "I have good news and bad news. Which do you want to hear first?"

"What's the good news?" Clary asks, one eye on the boys and the other on Magnus.

"Well, good news is- I finished the cure for those three." He points at the kids (and Simon).

"And the bad news?" Simon pats Izzy on the back absently.

"My outfit is ruined." Magnus proclaimed dramatically as he made his way over to the couch. Alec giggled as he flung himself dramatically onto the cushions, getting up from his spot on the floor to sit on the couch beside him and pat his knee, "Thank you Alexander."

"That's the bad news?" Simon wraps an arm around Izzy to steady her as he stands, "Doesn't seem that bad to me."

"Not that bad? This shirt cost more than a month's rent!"

"A month-?" Simon looks dubiously at the shirt Magnus is wearing, taking in the simply looking designs and plain cut.

"I wouldn't be caught dead in knock offs," Magnus proclaims, ruffling Alec's hair, "This is genuine Gucci."

"Can't you just-" Clary makes a waving motion with her arms.

"Of course I can, Biscuit." Magnus rolls his eyes, "But after I use magic to clean things, they're never quite the same."

"All magic has a price," Alec recites, and Magnus grins leaning forward to gather the smaller version of his boyfriend into a hug.

"I'm gonna miss this cutie." 

Clary frowns, the implications of finishing the cure just setting in. She glances between the children, noting that Simon is also frowning.

"Man, I didn't think of that," Simon pats Izzy's back affectionately.

"They're so cute like this, even if they are a pain in the butt." Clary sighs, watching as Alec presents his drawing to Magnus.

"This is the best drawing I've ever seen!" Magnus admires the childish art, holding it up to look at it before setting it carefully on the side table and turning to Alec with a sparkle in his eye, "Even better than Michelangelo."

Alec's eyes are wide, although Clary's pretty sure he has no idea who Michelangelo is. 

Jace gets up then, setting his drawing aside.

"Can you fix things now so I can go back to my dad?" Clary winces at his wording.

"I suppose we had best get started." Magnus sighs, gathering up Alec in a hug. Alec pats his cheek.

"Don't worry, I'll still like you," He tells the warlock innocently, and Clary coos internally as she gathers up Jace. Simon shifts Isabelle onto his hip.

"Well, come on then, step into my office." Magnus tells them, leading the way with Alec's hand clasped in his. The oldest Lightwood's eyes are wide as they step into the room, so different from the rest of the house.

Clary glances around, registering the odd assortment of (what she assumes) are spell ingredients and old looking books in foreign languages scattered around various shelves. There's an honest to god cauldron bubbling away in the middle of the room, perched delicately on top of a portable cooking range (which may and/or may not have come from Bed, Bath and Beyond).

"Alright then," Magnus claps his hands as soon as Simon and Izzy enter the room, and the door closes itself behind him, lights dimming and a blind sliding down to cover the window. "The procedure for this is pretty simple. The kids just need to drink the potion, and voila. It'll take about ten minutes to take effect, and their clothes won't change with them. Might I suggest that Clary take Isabelle into the first guest room, and Simon can take Jace into the second room so that their change can be relatively private? They'll be a little disoriented at first, which is why we can't leave them alone. I've taken the liberty of 'borrowing' a couple sets of clothes for them, which you'll find on the beds."

"I don't know if I should-" Simon starts, glancing over at Jace.

"Nonsense, it'll be fine."

"What about Alec?" Clary asked.

"Oh, I'll take care of him," Magnus grins, and Clary frowns at him. He shrugs. "It's nothing I haven't seen before, and I doubt he'd be comfortable knowing that either of you two were there."

"Magnus is a strawberry, remember?" Alec adds on, and Magnus pats him on the head again.

"Alright…" Clary glances at the smoking cauldron nervously.

"Who wants to go first?" Magnus lets go of Alec's hand to grab a ladle and fills three plastic cups with the potion.

"Ooooh me! Me!" Isabelle pipes up, and Simon has to put her down to keep from dropping her.

"Alright then, Isabelle." Magnus takes one of the cups and carefully helps Izzy drink it, watching as she makes a face. Simon watches her sadly.

"I'm going next." Jace announces, and Alec frowns.

"No, me!"

"I'm going!"

"I'm going!" 

Clary sighs. Of course.

"How about you drink the potion at the same time," Magnus suggests, setting down Izzy's cup and directing her towards Clary.

"Fiiiiiine," They chorus, both of them stepping towards the warlock. Clary sends a relieved look at Simon, gathering a sleepy Isabelle into her arms with a heave.

"Now, be very careful not to spill, and make sure you drink the whole thing," Magnus cautions, handing the cups over to the boys. Alec nods, and they both down the cups, eyes immediately starting to droop.

"They'll be back to their normal sizes in less than ten minutes, and I can finally get rid of the childproofing!" Magnus grabs Alec's shoulder when he wobbles, and props up Jace reluctantly, "Simon, come get this one."

"You know, for a powerful centuries old warlock, you are very easily defeated," Clary teases as Simon collects Jace.

"I don't think childproof cabinet locks are among most people's weapons arsenal," Magnus tells her with a huff, "I think I'm safe."

She grins, shifting Izzy on her hip.

"Best get to the spare rooms. I'm gonna take Alec to my room, since his clothes are in there." Magnus tells them, lifting Alec up into a bridal carry.

"Going-" Clary says, holding Izzy one armed to open the door and let them out. She blinks at the brighter light in the rest of the apartment for a second before heading into the spare room. She lays Izzy down on the bed, her eyes already closed and breathing deeply in sleep.

"This month has gone by slowly, but also super fast," Simon's standing in the doorway, pulling a sleepy Jace along beside him. "I'm not gonna miss demon catch, but Isabelle was pretty cute." 

Jace frowns up at him blearily, and Clary grins as Simon awwws.

"Admittedly, Jace is pretty cute when he's not glowering at me like I personally murdered his entire family."

"Better get him to bed before he passes out," Clary tells him with a snicker. Simon complies.

She hears the door to Magnus's room closing, and Simon is already pushing Jace into the second spare room when she gets up to close the door. 

Now all she has to do is wait.

**Notes for the Chapter:**

> I lied, there's still one more chapter to go.


End file.
